Receiving circuit



March 22, 1932. G. R. EATON ET AL RECEIVING C IRCUIT Filed June 50, 1927 plification;

Patented Mar. 22,3 1932 Our invfefntion relates to adio receiving;

feature ofour invention is the provision of an.inductiyely controlled radio frequency amplifying circuit receiwngits operating power from a sourceofalternating current.

A further feature of our inventin, is the audi0n tube for providing avariable grid bia's for said tube when'such tubeis used inasso,

ciation with a source of alternating, current l52s'upply- Another feature of. our: ini erition is: the

' provision of a receivingset having :t1bes using a. source of altrnatmgcurrert supply for ;Ernishing the c'athodes of the tbes with 2o? heating current, the plates of the tubes with plate current and the grids of part of the tubes wth a Variable grid jptentiallg Another feature of ourinyention is the provisin of a variablefg rid potentia l iieis for co1itrolling the Volume outputo foui inductiv ely controlled "receiving circuit. using au diors "of the alternating;curent type.

Still another feature of our inieiitio'n is the provisin of anlindictivelyf controlled radio rectly connected to the oscilltion collectoi.

Another eatuie ofui inventio'n isf the pr vision of blancifig means iii" conjunc'tionwith an nductiyely controlled radio receiviig set using a complete alternatmg current source= l A still further feature of oi' inyention is the provisin of aii"inductively controlled radio receiving circuit operating fromsource of alternating current, supply and 'ha'viiig a variable resistancein associationwith the of supp cathodes of certain of the udi6ii' tbs for 7 vision of'an inductiyely contiollediadio amplifier having {stages of different character and multiple cont'rlled indct'a'c'e devices forsuchstages, u y

Fr a better undeistiidihgf oir"'ien receiving circuit liaying"its. first stage di' Another 'feature of our'inventi isthe pro- 1927. Serial N0.- 202,492.=

former used with our invention. A

Referring to the drawings it will b'enoted that we illustratea -radio receiving crcufitin cluding inductively controlled radio fre-r quency amplifiction, detection and audio frequency amplification. A The. entire power used for. the"set is derii ed from a source of alternating Current without the use of any batteiies whatever. A 7

Theaudion tubes 10', 11, 12, 13, 145 and 16 are ofthe type in which the cathode is rendered active by1neans of:a heater resistance connected to a source oflternating curreit; Each tube coinprises a cathode, provided with a coting to increase the electron cinissin, a heatr Wife, a gridahd ap1ate; The haters are not directly electrically connected with the cathodes. For a furtherunderstanding of the construction: of such' '{a' tube'reference may behad'to co-pending a plication S. N. 225,053, filed October 10, 192%:

The radio"fiequency amplifying systemis of the inductively controlled type in which the tap switches 17, 18, 19, 20 nd211are gang or ,n'riultpl controlled and. the rotors of" the couplers and ,induc tance 4'areg'ai1g or multiple controlled. The multiple control switches change the indetance oftherwindings by steps aiid the rotors of the coils,

r which are mltiple controlled, controlthe.

in'ductance continuously between steps. For amore Complete understanding of the construction and functioningof such 'apparatus, reference may be had to co-p'ending"applica; tioii'S. N."26 835fi1d Apri130,1925 l The characte'r2 represents the Ordinary anteni1a or Collector device which is connected through a compensating j condenser 3to the Variable inductance: 4. The 'va'r'iab1einduc tance 4'consistsjo'f' astatoi portion and r) tor portion. The sttor portionincludes the Fig. 3-diagraminatically illustrates a trans-z r portion of the winding which is tapped and connected to contact points, which points co operate with the wiper 17. The rotor portion includes a part of the winding and is rotatably adjustable to further change the inductance of the winding 4. The compensating condenser 3 may be used to adjust the set to different lengths of aerials and after once set for a certain aerial need not be thereafter adjusted.

The couplers or transformers 22, 23, 24 and 25 comprise primary windings 26, 27, 28 and 29 and secondary windings 30, 31, 32 and 33. The couplers or transformers include a stator upon which the primary winding is wound and part of the secondary winding, the balance of the secondary winding being wound upon the rotor, The rotors are mul tiple controlled along with the rotor of the inductance 4. The balance of the secondary winding is includedon the stator in inductive relation to the primary winding, and part of the secondary winding on the stator is tapped and connected to terminal points for cooperation with the contact wiper. contact wiper 17 of the inductance 4 and the contact wipers 18, 19, 20 and 21 are multiple controlled by a single device.

Figs. 2 and 3 respectively illustrate diagrammatically the structure of variable inductance 4 and transformer 22. The variable inductance 4 consists of a stator a and a rotor b adapted to be rotatod within the stator a. The portion of the winding on the rotor is connected to the portion of the winding on the stator. Part of the winding upon the stator is provided with taps for cooperation with the switch;wiper 17. The transformer 22 comprises a stator portion c and a rotor portiond. The stator portion supports the primary winding 26, the balancing winding 44 and part of the secondary winding 30 which winding is provided with taps for cooperation with the switch wiper 18. The rcmaining portion of the secondary winding is supported by the rotor tube d.

Bridged across the inductance 4 to the of the devices change the inductance of the same to tune instations in the different wave zones. Condensers 35, 36, 37, 38 and 39 are preferably made variable, but after once they are adjusted to line up the stages, they are locked in their adjusted positions and do}not need to be thereafter changed. The tuning in of stations is entirely accomplished by moving the multiple controlled switch lovers The to make contact with their switch points of a desired wave zone and thereafter the multiple controlled rotors are operated to bring in the desired station. The volume of the signal reproduced is controlled by moving thewiper 94 over resistance 95 to control the Y grid bas of the tubes 10, 11, 12 and 13.

Tapped between the condenser 3 and in- The other radio frequency stages are connected in a like manner except that the connection from the Secondary-of coupler 25 to the grid of tube" 14 includes a grid leal: 42

and a grid condenser 43 and no balancing winding. The winding 44 of transformer or coupler 22 and the condenser 45 are connected in a balanced bridge circuit to prevent inherent feed-back and oscillation. Likewise, the winding 40 and condenser 46 are used for the same purposes in connection with the audion 11. The windirig 47 and condenser 48 of audion 12 and the winding 49 and condenser 50 associated with audion 13 are used for the same purposes After the Vheatstone bridge circuits are once balanced by adjusting the balancing condensers, these condensers are locked in place and need not thereafter be adjusted. Vhile I have shown only one ground connection it is understood a plurality of ground connections may be used, and the shielding of the set grounded.

The transformers and 56 are audio fre quencyi transformers having iron cores and are used inconjunction with the audion amplifier tubos to produce audio amplification. The condenser 57 is a by-pass condenser. The plate of audio tube 16 is connected through the winding of an iron core transformer 58 to the positive side of the B or plate supply. The secondary 59 of transformer 58 is connectedto the loud speaker device.

' Referring to the apparatus shown in the lower left hand corner it comprises an iron core transformer 60 having a primary 61 connected across a source of alternating current (not shown) by means of its conductors 62 and 63. Brdged across the conductors 62and 63 are condensers64 and 65, the center tap of which is connected by means of conductor 66 to ground 41. These condensers drain off disturbing noises which may come in over the alternating current power leads. The transformer 60 is provided with a secondary winding 67 which supplies a step down voltage to the heater elements of the different audion tubes over leads 68 and 69. The center point 70 of thissecondary winding is grounded at 41 for eliminating disturbances. The secondary winding f-isz .con nected through;a variable-resistance :731 to the filament or cathodenofaa rectifier device 74:. The full wave rectifier 74:- has a:pair ofi.plates 7 5. and 76 r connected :tojthe Opposite tenminals of secondary 77. -The CBItI'LL ;point 0f sec.- ondary 77*is connected;to;grond:4l and forms the negative-terninabof;the;plate: current supply. Connected:to one ter'mina'l' of the filament of the=-rectifier. device74.at:80

age of the current connectedtothe. plates of audion tubes 10,,11,.12 and:13;to a predeter: 1nined voltage. Theplate of the;audion tube 14; is connected through the resistance 91 to the B supply lead 84, and the resistance9l acts to reduce the voltage of the plate current to a predeterminedvalue. A

The plate of audion tube 15 is connected to theprimary of audio transformer 569 and through resistance 92 to theB supply lead 84, and the: plate: of: audi0n tube 16 is :connecteduthroughg the primary of audio transformer 258directlyto:thefull voltage supply y lead 84.

The cathodeof'tubez10is connectedythrough resistance93 of azpredeterininedtvalue to the wiper 94::associ-atedwith resistance95. Thecathodes 96, 97, 98 of: audion tubes 11, 312: and 13 are connected through: a resistance 99 to the v wiper 94, associated with resistance 95. By-pass condenser .100 is connectedacross fromthe one:terminal of the resistance 99 to ground and by-pass condenser 101 is con mected*frorn the other terminal ofresistance 7 99 to.ground Condenser l02 is connected 108 and ground 4:1.

from ground to vone:ter1ninal of resistance90.

Condenser 103 is connected :from one terminal of resistance 91to ground and 'condenser-104 is connected from one term1nal of res1stance 92 to, ground. .A resistance; 105 isconnected between cathode 106z0f; audiontube 15 and -.ground 41, and cor1denser i107is connected between cathode 106 and;ground P41. The cathode 108 oftube 16 is connected through resistances 109 and 105t0 ground 41;,and the condenser 110 is: connected, between cathode r Cathode 111 of tube" 1() being;connected through: resistance 93 ahdvariable. resist- 3 ance *to: groundthe potential ofcathode 1=11: isrraisedx with respect: to the-potential of thegrid,ethusmaking saidr cathode positive with refspect to thejgrid of the tube.l0 thereby providing a: negat ve ;grid ;bias. The grid return of audion tubes 11,2 12:and 13: are conv nected to:ground:andas the cathodes of these tubesare connectedthrough resistance99 and variable resistance95;to; ground the cathodes OZS&C],THbQS arepositivewith respect to the i grids of tubes 11,l2and13 giving to the tubes a negative' grid bias. The cathode of tube 4 s connected directly to ground as 'audion 14isthe detector. Since the cathode of tube 10 is connected through.resistance93 to the wiper 94 and thecathodes of tubes 11,.12 and -1 3aie;connected through resistance 99 to the wipei 94, which may be adjusted relative to resistance 9,5, the difi'erence of potential betweengthegrids and cathodes of these tubes maybevaried soas to providea variable negative:grid bias for theggrds ofthe tubes 11,512 and-13. 1The resistance 105 con:

nectedbetwe en the cathode 106oftubel5 and ground,provides the necessary negati37ebias for theggrid of tbel5 and the resistance 1'09 provides the necessary grid .bias for. the; grid of the tube 16. '.With this,arrangementthe usual C batteris for providing the neces .sary grid biasar;eliminatedaridthebiasing is accomplishedzby-the said resistances The :means for Varying the resistance in thecathode circuit's of audions 10,11, 12*and 13 provides means-for varying, the volume outputof the'receiving circuit. This means provides a very efiicient anddesirable,method of controlling the volume :output, of za; set .usingtubes of the character described above.

y It beingrcmemberedthat the switch wipers 17 to 21 inclusive change.the inductance',in

comparatively coarse steps while the rotors of inductance;4 and transformersf26{- 27, 28

and 29 vary the inductance within the steps of inductance between taps, to tune ina sta tion of a predetermined frequency and wave length, the wipers are set on the contactpoints i Then the inductance of the windingsis varied minutely by the rotation of the rotors of the coilsuntilthecombination oflthe inductances v and bridge condensers are such as to per nit" the frequency; of .the, desired wave length to Wiper 94 is adjusted toregulatethe grid bias oftubes 10, 11, 12and l3untilthe desired T120- volume of the received signal is produced .f

On the longer wave lengt hs the coupling between the primarywindings onthestator w and the secondary windings is increased so that the.amplification Will be constant over theentire wave band. It is not believd neccesary to :amplifyin detail the manner::in which the incoming ,oscillations aregreceiV,ed

bythe Collector2 and are amplifid the receiving circuit, other than to state that. the -oscillations are directly operative upon which include the wave length of the,band

within which the .desired signal: appears.-

of alternating current.

the grid of the tube 1 0, which is connected directly to the aerial or collector device, and

from the tube 10 the oscillations are efiectve cuit is from the aerial 2 through the grid 1'12 to the cathode 111, and balancingWinding 44 is connected between ground and the cathode 111, while in the other stages of radio fre quency amplification the input circuitis across thesecondary 30, 31 or 32andits bridged condenser 36, 37 or 38, extending through -balancing winding 40, 47 or' 49 to ground and back to the cathode 796, 97or 98, the balancing winding in this instance not being between ground and the cathode.

From theforegoing it will be apparent that we have provided a system Which uses no batteres whatever. The cathodes of the audions are rendered active through the medium of heater elements connected to as0urce L The anodes of the audions are supplied 'witha source of rectified filtered current and the grids are provided with biasing potential by means of re sistances, the grid bias of certain of the tubes being variable to control the volume output r of the set. The system is of the inductively controlled type having a direct feed in the first stage from the aerial to the grid of the audion tube and means are provided for mul tiple control by simultaneous adjstment of the several stages.

Vhile we have illustrated and described a 7 specific circuit arrangement in association with our invention, many other arrangemente diflerent than that described .m'ay be used, and it is therefore our desire to cover all such changes andmodfications as come within the spirit and scope of the appended claims.

Having describedour invehtion what we claim is new and desire to secure by United cillations, a grid and a cathode for each of Said audion tubes, a resistance connected between the grid and cathode of said radio amplifier audion for rendering said grid more negative than said cathode, a circuit coil of the connecting thegrid to the cathode of said rectifier audion, a second resistance connected between the grid and cathode of said audio amplifier audion for potentializing said grid, and a third variable resistance connected betweenthe grid and cathode of said radio amplifier audion to vary the difference of potentialbetweeh the said grid andcathode of said radio amplifier audion.

2. A cascade amplifying circuit including a radio amjolifier, a detector and an audio amplifier for amplifying and demodulating incoming oscillations, each of said amplifiers and said detector including a cathode, a grid and an anode, a source of alternating current, a heater for each of said cathodes connected to said source of alternating current, rectifying means receiving current from said source of current and fuinishing unidirectional current to said anodes, a grounded circuit con nected to each of said grids, a resistance con nected between the cathode of said audio amplfier and said grounded circuit for potentializing the grid of said audio amplifier, a resistance connected between said grounded circuit and one terminal of the uni-directional source of current, and another resistance con ,nected between the cathode of said radio amplifier and said second resistance for varying the potential of the grid of the radio ampli fier relative to the cathode of the radio ampl1fier.

3. A cascade rece1v1ng arrangement involving a plurality of stages of radio fre-7 quency amplification including audion tubes provided with indirectly heated cathodes and transformers connected to the terminals tubes and to animpedance, means for varying the inductance of said transformers and of said impedance to resonate the amplifier toreceive signals of desired frequencies, a source'of alternatirig current, a transformer connected thereto, a winding for said transformer supplying current to heat the cathodes of said tubes, a rectifier device, a second windingfor said transformer'supplyng current to said rectifier device, said rectifier device producing plate current for the anodes of said audion tubes, and resistances including a variable resistance connected between elements of said tubes and to said source of plate current to provide potentials for the grids of said audion tubes.

4. An amplifying circuit including an audion tube having an indirectly heated "cathode, an anode anda grid for said tube, a

heater for rendering said cathode operatve,

a source of alternating current connected to said heater for rendering the same active, an inductance bridged by a condenser connected bet w'een said grid and ground, a balancing winding connected between the cathode and said ground, a condenser connected between said cathode and said grid, said winding and condenser operating to prevent feed-back from said anode to said cathode, and a vari able resistance connected between said grid and cathode for varyingly potentializing said grid with respect to said cathode.

5. A cascade receiving circuit including a pluralityof audion tubes and transformers connected together to forma radio amplifier, an inductance, an aerial circuit connected directly to a grid of one of said tubes and to said inductance, primary and secondary windings for said transformers, condensers bridged across said secondary windings and said inductance, means for simultaneously varying'the inductance of said secondary windings and of said inductance connected to said aerial to resonate the radio amplifier to dsired frequencies, a source of alter nating current, means for 'supplying current from said source to the cathodes of said audion tubes to render the same operative and to provide plate current for the plates of said audion tubes, a resistance connected to elements of said tubes and to said source of plate current for establishing a difference of potential between the grids and cathodes of said audion tubes, and means for varying said resistance to vary said difference of potential between the grids and cathodes of certain of said tubes.

6. A cascade three section amplifier circuit including a radio amplifier, a detector and an audio amplifier, a transformer and an audion tube included inthe radio amplifier, said audion tube being connected to a wind ing of said transformer, a transformer and an audion tube included in said detector, said audion tube being connected to a winding of said transformer, a transformer.and

fier tube through the transformer associated therewith to said grounded Circuit, a second resistance, and a circuit extending from said grounded circuit through said second resistance to the cathode of said audio amplifier tubefor potentializing the grid of said audio amplifier tube.

Signed by us at Chicago, in the county of Cook and Stateof Illinois, this 28th day of June, A. D. 1927.

' GEORGE R. EATON.:

EARL RAY'HEATH.

an audion tube included in said audio am-7 plifier, said tube being connected to a winding of said transformer, a cathode for each of said audion tubes, a source of alternating current, a transiormer connected to, sa1d source of current and having a winding sup plying current to heaters for said cathodes,

a rectifier connected to a winding of said last transformer and supplying current to the plates of said audion tubes, a ground circuit connected to one side of said plate current, a circuit extending from the grid of the radio amplifier tube through a windirig 0f transformer associated therewith to said grounded circuit, a variable resistance, a circuit extending from said grounded circuit through said resistance to the cathode of said amplifier tube for controlling the bias of the grid, a circuit-extending from the grid of said detector tube through a Winding of the transformer associated therewith to said grounded circuit, a circuit extending directly from said grounded circuit to the cathode of said detectortube, acircuit extending from the grid of theaudiampli 

